1. Field of the Invention
This invention pertains generally to imaging of tissues associated with skeletal joints, and more particularly to identifying and/or characterizing medical conditions associated with skeletal joints, pain, or both. Still more specifically, it relates to using nuclear magnetic resonance (NMR) spectroscopy to identify, localize, and/or characterize chemical, molecular, structural, or other signatures related to medical conditions in tissues, such as degradation or pain associated with skeletal joints (for example spine).
2. Description of Related Art
Intervertebral disc degeneration (IVDD) is a leading cause of lumbar spine related lower back pain, a common medical problem that affects 60 to 80% of aging Americans. The intervertebral disc is a flexible fibrocartilaginous structure that supports forces and facilitates spinal movement. Healthy discs consist of three specific tissue components: 1) the annulus fibrosus, a collagenous region tightly packed circumferentially around the periphery of the disc which allows for pliability; 2) the nucleus pulposus, a hydrated, proteoglycan gel located at the center of the disc, which when compressed expands radially and braces the annulus fibrosus to maintain stiffness and prevents the annulus from buckling under compression; and 3) a cartilaginous end-plate that separates the nucleus from the adjacent vertebral bone.
Disc degeneration is characterized by a complex series of physical and chemical degradative processes. The extent or severity of IVDD is most commonly described clinically using the Thompson Grading Scale, where following a set of parameters, a x-ray radiographic inspection of the disc is conducted and the gross morphology is used to determine the extent of degeneration. One research group has concluded that changes to the mechanical properties of the intervertebral disc suggest a shift from a “fluid like” behavior to a more “solid like” behavior with degeneration. Fixed charge density (FCD) and the biochemical environment of the surrounding water have also been shown to greatly influence degeneration; as highly charged proteoglycans attract water and cause the tissue to swell, disc pressurization and spinal load support are directly affected. Differences in the Thompson Grade are reflected by changes in the concentrations of constituents such as collagen and proteoglycans in both the annulus and nucleus. It has been proposed that biochemical degradation, upregulation of genes associated with collagen matrix degradation, and the cumulative effect of mechanical loading, all stimulate the degenerative disc process.
Identification and characterization of disc degeneration thus involves a wide array of technological developments and efforts over many years. Yet, an adequate, repeatable, non-invasive system and method to characterize factors related to pain, pain generation, or disc degeneration has yet to be provided as a useful medical tool.
It is also well appreciated in current medical practice that pain is a remarkably difficult phenomenon to diagnose and localize. This is in particular the case with respect to skeletal joint pain, and in particular back pain. Whereas certain targeted pain relief therapies may be made available, such as directed energy sources to locally ablate painful nociceptive nerves, the identification and localization of where to treat is a critical pacing item that often falls well short of providing the requisite specificity. As a result, the ability to successfully target such therapies in overall pain management is extremely challenging at best.
Degenerative disc disease, while a predominant cause of debilitating back pain, is however only one example of medical conditions in dire need for better tools and methods to characterize and localize the condition in order to appropriately direct therapies. Chronic back pain, for example, may result from several underlying root causes. These causes include, for example, vertebral compression fractures, degenerative disc disease, and disc herniation. In addition, other joint pain, such as of the spine or other skeletal joints (e.g. knuckles, ankles, knees, hips, shoulders, wrists, elbows) may also be the result of many different underlying causes (or combinations of them), and may also be very difficult to localize sufficiently to direct localized therapies. Pain associated with any or all of these joints may be located at the connective or cushioning tissue of the joint itself (e.g. the disc for spinal joints), or within the bone, or at transitional areas (e.g. the end-plates of vertebral bodies bordering discs).
A substantial need exists for improved non-invasive tools and methods for identifying and characterizing the degradation of tissues in the body. This is in particular the case with respect to skeletal joints, in particular intervertebral joints of the spine, and further in particular in and around the intervertebral discs themselves.
A substantial need also exists for improved non-invasive tools and methods for identifying, characterizing, and/or localizing pain within the body. This is also in particular the case with respect to skeletal joints, in particular intervertebral joints of the spine, and further in particular in and around the intervertebral discs themselves.